Apparatus for the propagation of music and other correlated sounds



June 1.o, 1930. A. H. MARKS 1,762,449 I APPARATUS F'ORv THE PROPAGATION OF MUSC AND OTHER CORRELATED SOUNDS Filed Jam 15; 1927 sheets-sheet 1 June 1o, 1930. A. H- MARKS 1,762,449

APPARATUS FOR THE PROPAGATION OF MUSIC AND OTHER CORRELATED SOUNDS June 1o, 1930. A f A. n. MARKS 1,762,449

APPARATUS FOR THE PROPAGATION OF MUSIC AND OTHER GORRELATEIDl SOUNDS Filed Jan. 13, 1927 S'Sheets-Sheet 5 T//rre -6ecs.

Patented June lO, .L

@UNITED STATES PATENT ori-Icag y ARTHUR H. MARKS, OF NEW YORK, N. Y., ASSIGNOB TO SKINNER ORGAN COMPANY, OF BOSTON, MASSACHUSETTS, A CORPORATION OF MASSACHUSETTS AJPPARATUS Fon THE PROPAGATION oF MUsIc- Ami OTHER CQRRELATED SOUNDS Application med Janaury 13,1927. serial No. 160,899.

v My invention relates vgenerally to the art of sound transmission and more particularyly to apparatus wherein rare factions and condensations of a compressible medium are translated into electrical undulations for propagation by broadcast or Wire connection to widely scattered or distant points. This energy is ultimately retransformed at the receiving station -into sound impulses having characteristicsy approximating the original vibrations. However, the invention described hereinafter is directed more to tlie primarytranslation, i. e. thechange in energy from acoustical to electrical and contemplates the faithful representation in the form of current undulations of the various n combinations of sound waves emitted bythe original source. Now, it appears that the I difficulties attending the dissemination of music by broadcast have centered largely about the primary translation and in particular to the process of converging into one or more receptive means, the acoustical effect of the many tone combinations and characters. This means ordinarily. comprises several microphones placed externally to the instrument. Under these conditions, the diaphragm, usually a flexible member, is constrained to vibrate either at a frequency falling within an extremely Wide range or at -a combination of several of these frequencies; in any case, themovement of diaphragm may'only approximate the Wave form of the impinging sound impulse. .Thesediiticulties are enhanced in the case of a pipe organ which ordinarily has extensive lay-outand is exceedingly rich in the vari- -oustone colors, pitch and volumatic changes,

ly effectuated by shutters under the control portrayin of pedals and/or draw-knobs, it is apparent that microphones placed externallyl to the instrument areincapable of accurately registering' the total range of manifestations expression, moreover, the baille method o controlling sound intensity'is not i without ldistortion and in the case of large to the 4bulk and expense of the instrument,

and tends to reduce the dependency of operation. In considering distortion, one must not overlook the fact that there is ever present attenuation of the electrical Wave output Whether propagated through wire or by radio the effect of which isto favor certain frequencies such that the subtleness of notes havingcomplex tone character is often obliterated during the process of transmission.

In order to further the favorable reception of organ recitals or renditions, I pro-` pose to adapt the present day organ to the peculiar needs of electrical 4transmission over great distances and particularly broadcasting. The modification of structure takes the form of a substantially complete acoustical isolation of'the various stops along a demarcation of frequency and also of effecting total or partial separation of the various tones by positioning each of a number of microphones in certain relation to the stops sounding at a definite frequency. It will be at once apparent that the presence of substantially sound proof compartments lends the structure readily to electrical amplification individual to any number of stops andas offering convenience in the control of volume from the console and a simplification of the instrument as a Whole. Furthermore,lby vproviding as far as possible the usual arrangement of manuals, stops,

barrier between the organist or performer and his music rendition. By providing a receiver nearby that registers the synthetic" electrical effect of the various-stops either at a distant receiving station or prior to transmission, the organist is the better able to judge as to the proper place and amount of expression or other 'effect in order to render an accurate interpretation of a musical work to the distant audience.

Accordingly, the primary object of my invention is to improve the art of music transmission in general. A more specific object is to provide means for efficiently converting sound energy derived from a number of sources and distributed over a wide area, into the electrical equivalent for transmission and subsequent reproduction of the original sound aggregate.

.Another object is to procure at a distant point, the highest possible degree of fidelity of the original rendition. A still further object is to simplifythe organ structure without disturbing in appreciable measure, the

usual arrangement of console accessories. Further objects and features will be evident from `the perusal of the following description when considered in connection with the accompanying drawings in which like reference characters represent corresponding elements throughout the several views.

y Fig. l represents a section in plan of aY typical organ and by diagram, a number of receptive means with associated circuits adjacently disposed. tothe array of stops or speakers;

Fig. 2 is a continuation of the preceding View and shows partly in perspective and partly diagrammatic, the manual controls or console;

Figs. 3 and 4 illustrate a desirable mode of amplification Fig. 5 represents the characteristicy curve of a certain diaphragm showing the phenomenal change in amplitude at the natural frequency period; and

Fig. 6 indicates broadly the waveform of a few more common sounds emanated during a rendition of average compass.

Referring particularly to Fig. l, numeral l designates a number of pipes, stops or speakers comprising the usual tone families found in a representative organ. As' will be understood, upon the application of air under pressure, these stops are designed to speak at regularly established frequency intervals from 16 cycles per second emitted by the 32 pipe to 8192 cycles per second in the 3XL stop and even higher. From these figures it will be apparent thatlin proposing the faithful translation of the various sounds into current undulations, the tremendous range in frequency presents a problem of no little import. Nor is this all, for in the vorgan of average size, the tone character or timbre of the individual stops may vary all `the way from the squeaky little flute toA A the thunderous bass bourdon presenting a total variation in character quite beyond the erable compromise may be necessary in the case of pipes, the frequencies of which do not conform exactly to the arbitrary line of division.

These groups arethen acoustically separated from each other by partitions 2 comprising inelastic, sound absorbing, non- `resonant substance as sheet asbestos, plaster,

cloth layers or the like.' In the compartments thus formed, there is placed a number ofA microphones or other receptive means having an electrical output in common for convenience of transmission.

While it is recognized that particularly good results are obtainable by providing each stop with an individual microphone having special adaptation thereto, this structure being specifically embraced by my invention, I have found that satisfactory reproduction is quite feasible with a reduced number of sound receivers., Having effected aldivision of stops on a predominant frequency basis, those in each compartment are y then arranged in a gradat'ion of wave character as determined electrically by oscillograph or other method. Each graduated series, the components of which sound at approximately the same frequency, is then divided into a plurality of sub-groups having a number of speakers determinable by the maximum latitude of character falling completely within the response range of a single vibration diaphragm. In arranging the sub-divisions, the difference in distance between the centrally disposed receptive means and the nearest and farthest removed stop must be considered; thel smaller the difference, the greater will be the fidelity of response in the receptive means. Taking into account the range of tone character and difference in the spacial relation of adjacent llO speakers with respect to a given'diaphragm,

it will be apparent that as progression is made toward the lowermost frequency, the number of stops per microphone should decrease. Thus, in Fig. l, this" condition is exemplifiedv by illustrating one microphone within response range of ivestops sounding at an 8192 cycle note, while atthe other end of the frequency scale a receptive unit accommodates only one or two pipes. The necessity for the change in the proportion of-stops per mircophone is illustratively emphasized in Fig. 6, wherein curves a and b represent'the sum total of fundamental frequency and overtones forming the characteristics of two representative notes sounding at approximately the same fundamental in the low portion of the scale. Curves c and d likewise apply to stops speaking at IGSPOIISG.

the upper portion of the musical` range. From an inspection of these graphs, it will be seen that the net effect of the overtones in shaping the charactert of sound is more pronounced as the frequency is diminished or en h of pipe becomes greater; this fact is str1 'ngly brou ht out by the .difference in areas between t e sets of curves. A

`Furthermore., in adapting a microphone by desi n to a note or group of same, it is prefera le for well-known reasons to remove, as faras possible, the resonant peak inherent in' the diaphragm and associated parts as shown in Fig. 5 from that of the predominating frequency in the particular note or group.- The material and dimensions of the diaphragm also should be such as to allow a movement closely approximating the curve cnvelopin gregate of the notes wlthin the range of In short, each microphone must have adaptation to its individual load.

While directions concerning the relative positions and adaptations of the microphones seem more or less precise, 1t 1s to be understood that in the absence of an enclosure state,

for each stop which may prove impractical from either of an acoustical, structural or cost standpoint, the theoretical determinations call for modification in practice due ortions in part to substantial merging of of microphone response areas. owever, considering the musical effect as a whole I have found that'the stated methods o arranging theV stops with respect to a -smaller number of microphones effectuates a decided improvement in quality of tonal output.

how, as stated hereinbefore, I propose to electrically amplify the note issuing from each stop or a group of same, eliminating the necessity for shutters and for this purpose, provide a number of devices diagrammatically represented by rectan les 4. These devices which may or may not e individual to the microphones, take the form of the audion, well known for its distortionless amplification, and associated input and output transformers as shown in Fi 3. By rectangle 5, the contents of whic are illustrated in Fig. 4, I show another `form of audion circuit which is applicable to the last stage of amplification within each compartment. Inasmuch as the exact nature of the am lifiers is self-explanatory and known to t e art, a lengthy descriptionof the same appearsl'unnecessary. Suffice to hat the amplification ratio of both ty es of audion system is controlled with vsultable means by the familiar nexpression yshoes 6 and/or draw-knobs 7 at the console.`

This means may take the form of variable A resistances effectively inserted inthe plate preferabl the character ag- 1 ical and/or electrical system of linka e.

The pair of resistances 15 and 16 should e A.

controlle by draw-knobs 7 and expression shoes 6 respectively in the manner shown. If desired, instead'of utilizing two resistances, one may limit the function of ythe of a coarse and fine gradation draw-knob to a make and break circuit ar- A l. the amplifiers, in fact, many arrangements for controlling the latter are readily vadaptable. By rectangle '8, I'indicate any wellknown'switching arrangement whereby the current passing through a circuit diagrammatically indicated b ysingle condu tor `9 may effectively contro any one or all of the electrical connections passing out from the rectangle.

It is to be understood that manuals 10, pedals 11, and draw-knobs 7 each have their usual air control function, while the latter may take on an vadditional function and with the expressionv shoes re ulate either, jointly or severally, the am li cation of the various tone characters. oreover, it will be obvious that my invention is not limited to the thermionic 'amplification structure shown or to the described mode of operating same as' various modifications will sugest themselves to those skilled in the art.

owever, by Vreason of its faithful translation, compactness, simplicity and lending itself readily to a multi-unit system, the audion appears to have considerable advantage over other types of amplifiers known to the resent art.

As indicate in F ig.4 1, the combined outtory effect from the primary rendition. By vemploying receiver 14, h e is enabled to obtain by localized radio transmission a secondary rendition by which to judge the musical synthesis at the distant receiving station and if necessary, correct any de'- ficiencies of effect. The subject matter last mentioned is disclosed and claimed broadly in-my Patent No. 1,596,984, granted August 24, 1926, andy entitled Method and appa ratus for broadcasting.

From the foregoing, it will .be apparent that inthe proposed instrument, as 1nodi, fied, the tremendous range between the grandeur of -the full organ and its softest voice representing a complex and ever varying proportion of tone/color, frequency and volume is preserved inmarked degree during the primary translation process.

Wliile exemplifying my invention by application to a pipe organ, it Would seem' that the disclosed subjectmatter may be embodied in many other forms than those shown and described, and I therefore impose no limitations of structure on the invention except as may be implied from the scope of the appended claims.

I claim:

l. In an instrumentality for producing sounds of various frequencies and complex characters, a plurality of soundeproof compartments, each containing al group of speakers sounding at approximately the same fundamental frequency, each group being arranged in a gradation representing variations of tone or timbre.

2. A pipe organ comprising speakers arranged in a plurality of groups, each containing stops sounding approximately the same frequency but varying in timbre and means for selectively translating into electrical energy the acoustical effect derived from a certain numberof stops in each group i less thanthe Whole group.

ber provided with one or more microphones connected to an amplifying device for translating the sound impulses into amplified current undulations.

5. A pipe organ comprising at least one stop of each tone family desired enclosed in an acoustically isolated chamber, each chamber provided with' one or more microphones connected to an amplifying device for translating the sound impulses into ampliiied current undulations and means located on console for both controlling the operation of each stop and amplifier.

6. A pipe organ comprising at least one stop of each tone family desired enclosed in an acoustically isolated chamber, each chamber being provided with one or more microphones for translatingithe sound impulses into current undulations, each microphone being particularly responsive to a predetermined range of frequencies.

7. The method of adapting a pipe organ to efficient transmission of music which comprises dividing the speakers along afrequency demarcation and selectively translating into electrical energy the acoustical effect derived from each division of speakers. 8. The method of adapting a pipe organ to efficient transmission of music which oomprises effecting an acoustical isolation between groups of stops, arranging each group in a gradation of stops representing variations of tone, and selectively deriving the tonal output of a predetermined 'number of stops in each group.

9. The method of adapting a pipe organ to efficient electrical transmission of music' which comprises effecting an acoustical isolation in substantial degree between groups of stops, and selectively translating into undulations of current the acoustical energy derived fromA one or more stops in each group.

l0. The method of adapting a pipe organ to efficient transmission of music which comprises dividing the speakers along a'frequency demarcation, selectively translating into electrical energy the acoustical effect derived from each division of speakers and controlling the volume of the energy so transmitted from each division.

Signed by me at New York city, N. Y., this-6th day of January, 1927.

ARTHUR H. MARKS. 

